I have noticed that the properties of the Construction Pylons from SE do not keep their Supply, Construction or Network reach properties when upgraded to a Lighted Construction Pylon.

I'm having this issue as well. Still running version 1.9 as I'm writing this comment.

Can confirm issue with 1.10 as well.

having this problem my self now. my base is far to big to replace all my power poles :(

Also having this issue

Going by composites.lua, there's currently no way SE can be made aware of variants to any of the pylons.
Unless Earendel adds an API to register additional poles I wont be able to make SE aware of LEPP's lighted variants.

If you want the functionality you'll have to use the normal SE versions.
LEPP 1.10.1 will have se-pylon-construction and se-pylon-construction-radar blacklisted to stop LEPP generating useless variants.